How accurate are dating scans in pregnancy
These are basic calculations such as the length from crown to rump (head to the end of the bottom), the femur length (longest bone in the body), and the head circumference.
Some of these and other measurements are most useful after 13 weeks, which is beneficial for a late dating scan.
LMP is only used until the dating scan as it's the best guess until they measure the baby.
The scan measurements are supposed to be accurate to within a couple of days.
anyway scans are only a guide on gestation, i know the EXACT date i ovulated (as i used a donor) so i was charting my temps and scans can be 5 days out either side.These help to ensure the pregnancy goes smoothly, and to identify any problems ahead of time.The dating scan is generally the first ultrasound that every mother-to-be will have.Both pregnancies we were sure of the date (the first time I was working away loads and this time hubby was working away, so we kinda only had the one opportunity lol! With my daughter the LMP was definitely wrong as my periods were irregular and the scan told us the exact dates we had worked out ourselves.With this pregnancy however the scan dated conception 4 days BEFORE we dtd.